After the P3: Late executive processes in stimulus categorization

Abstract

Two experiments examined the hypothesis that dual systems of stimulus evaluation for categorization can be observed in event-related potentials: one whose duration is indexed by the latency of the P3 component, and a second evident in a later frontal potential. Subjects categorized artificial animals by a "two out of three" rule. Stimuli with two visual features of their own category and one feature of a different category (i.e., near the boundary between categories) elicited very prolonged reaction times as compared to stimuli with three features from a single category. This RT delay was not accompanied by a delayed P3, suggesting that the P3 indexed only a first pass of stimulus evaluation. The near-boundary stimuli elicited more positive potentials than far-boundary stimuli at prefrontal and frontotemporal sites, suggesting that a secondary stage of stimulus evaluation was triggered when detection of single features or simple conjunctions was insufficient to support a correct decision. The frontal potential that was sensitive to categorization difficulty was of opposite polarity to frontal potentials previously observed in manipulations of working memory. The roles of frontal executive processes in categorization and memory tasks are discussed.Most cognitive theories of categorization posit multiple systems for learning object categories and categorizing objects (Ashby, Alfonso-Reese, Turken & Waldron, 1988;Knowlton, Squire & Gluck, 1994;. One important distinction is between categorization based on logical rules and categorization based on similarity to prototypes or exemplars (Allen & Brooks, 1991;Erickson & Kruschke, 1998;Johansen & Palmeri, 2002; Nosofsky & Palmeri, 2002;Smith, Patalano & Jonides, 1998). Several lines of evidence suggest that rule-based categorization is slower than familiarity-based categorization and places greater demands on working memory and selective attention (Smith et al., 1998). Consistent with this argument is evidence that the two strategies have different neural correlates, with rule-based categorization recruiting prefrontal and parietal cortices to a greater degree (Koenig et al., 2005;Grossman et al., 2002;Patalano, Smith, Jonides & Koeppe, 2001). Although hemodynamic imaging methods have offered some insights into the anatomical correlates of categorization strategies, event-related potentials (ERPs) offer complementary insights into the temporal characteristics of neural activity in addition to coarse-grain information about the brain regions engaged. Below, we review two distinct components of the ERP that appear to reflect temporally and neurally distinct Correspondence: Jonathan Folstein, Psychology Department, Vanderbilt University, 301 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203. jonathan.r.folstein@vanderbilt.edu. 2 We also analyzed response-locked ERPs relative to the same pre-stimulus baseline used for the stimulus-locked averages (see Verleger et al., 2005 for a similar procedure), with results much like the analyses reported in the main text....

Cognitive changes in conjunctive rule-based category learning: An ERP approach

“…Results revealed a larger late positive slow wave for difficult compared to easy categorization stimuli, confirming that processing differences exist based on stimulus difficulty and taking us a step past what behavioural research can tell us. This is consistent with other research showing that larger, late positive ERPs are associated with classifying exemplars that are near the category boundary and thus more difficulty to classify (Folstein & van Petten, 2011) , though they observed this effect primarily in frontal regions, whereas we observed the effect in central parietal region. This difference is not unexpected given the different nature of the category tasks being examined.…”

“…As such, ERPs are well suited to study how participants process stimuli that follow the rule, how they process stimuli that do not follow the rule, and how participants react to feedback. For example, Folstein and van Petten (2011) collected ERP data from participants in a multi-dimensional rule-based category learning task in order to analyze the difference in frontal-parietal waves when participants were classifying stimuli that were near the category boundary versus stimuli that were far from the boundary. Near boundary stimuli are less typical and more difficult to classify because they possess features that are common in the opposing category.…”

Lexical versus conceptual anticipation during sentence processing: Frontal positivity and N400 ERP components

“…Error bars show standard errors. 2001), the parietal maximal of the P600 elicited by syntactic errors or some varieties of semantically problematic words (Friederici et al, 1996;Hagoort et al, 1993;Kim and Osterhout, 2005;Kuperberg et al, 2003;Osterhout and Holcomb, 1992;van Herten et al, 2005), or the frontopolar maximum of late positivities observed in some episodic memory and nonverbal categorization tasks (Folstein and Van Petten, 2011;Kuo and Van Petten, 2008;Senkfor and Van Petten, 1998). One might be concerned that the observed frontocentral topography is an artifact caused by temporal overlap with a more posterior N400, such that the positivity is more visible where it is not canceled by an overlapping N400.…”

The activation of visual face memory and explicit face recognition are delayed in developmental prosopagnosia

“…The explicit recognition of a particular individual face is associated with a sustained broadly distributed positivity that emerges around 400 ms after stimulus onset. This late positive component (P600f; Gosling & Eimer, 2011) is similar in its timecourse and scalp distribution to the P3b component that is observed in many targetnontarget discrimination tasks, and is assumed to be linked to the allocation of attentional resources during the explicit categorization or identification of task-relevant stimuli (e.g., Folstein & Van Petten, 2011). In our earlier study , P600f components were only elicited on trials where DPs correctly reported a famous face, in line with the view that the P600f reflects the conscious recognition of an individual face.…”